Group B streptococci (GBS) are being increasingly recognized as important human pathogens. In addition to causing meningitis, bacteremia, endocarditis, bronchopneumonia, arthritis, peritonitis, wound infections, abscesses, and urinary tract infections in adults, as many as 80% of group B infections occur in neonates (Jelinkova, J. [1977] Current Topics in Microbiology and Immunology 76:127-165). Approximately 30% of pregnant women have been reported to be colonized by GBS. Despite this high carriage rate, neonatal infection occurs with an incidence of only 0.5%, resulting in over 12,000 deaths annually (Lim, D. V., Morales, W. J., Walsh, A. F., and Kazanis, D. [1986] J. Clin. Micro. 23:489-492). Predisposing factors to development of disease are premature birth, prolonged rupture of membranes, overt maternal infection, and deficiency of type specific antibody (Boyer, K. M. and Gotoff, S. P. [1986] New England J. Med. 314:1665-1669). To date no one has identified a bacterial marker which would predict which streptococcal strains are more likely to cause infection.
The ability to subtype group B streptococci more comprehensively may be of value in predicting which organisms could cause sepsis, in particular neonatal sepsis. Recently, a receptor for the Fc region of human IgA was reported to be expressed on the surfaces of some strains of GBS (Russell-Jones, G. J., Gotschlich, E. C., and Blake, M. S. [1984] J. Exp. Med. 160:1467-1475). Western blot analysis of proteins extracted from these strains by treatment with detergent indicated that it may in fact be the .beta. antigen component of the c protein marker complex which has the ability to bind to IgA (Russell-Jones, G. J. and Gotschlich, E. C. [1984] J. Exp. Med. 160:1476-1484). Since IgA is the primary line of defense at mucosal surfaces, such as the vaginal epithelium, the ability of bacteria to bind this class of immunoglobulin molecules in a non-immune fashion might interfere with effective clearance of these microorganisms.
A further level of sub-typing of group B streptococci, with respect to the c protein marker complex, would be desirable to identify potential pathogens.